Acute toxicity and sublethal effects of phenol on hematological parameters of channel catfish Ictalurus punctatus and pacu Piaractus mesopotamicus

Fernanda Dias de Moraes, Juliana Sá Leal de Figueiredo, Priscila Adriana Rossi, Francine Perri Venturini, Gilberto Moraes


Phenol is an aromatic chemical commonly found in domestic and industrial effluents that represents a worldwide concern in toxicology. When it reaches aquatic environments, significant damage in fishes is observed. The first aim of this study was to investigate the acute toxicity levels of phenol in Ictalurus punctatus and Piaractus mesopotamicus. The second objective was to evaluate the hematological parameters of I. punctatus and P. mesopotamicus after 96 hours exposure to sublethal concentration of phenol (10% of 96-hour LC50) and after post-exposure recovery period of 7 days. The main hypothesis of the study was that even sublethal phenol concentration could cause hematological alterations in fish. For 96-hour LC50 tests, both fish species were exposed to several phenol concentrations (in the range between 5 and 50 mg L-1) and the mortality were recorded after 24, 48, 72 and 96 hours. Phenol was notably more toxic to I. punctatus than P. mesopotamicus and the 96-hour LC50 values were 15.08 and 32.56 mg L-1, respectively. Sublethal exposure to phenol in P. mesopotamicus resulted in significant higher hematocrit level (Ht), hemoglobin content (Hb) and red blood cell count (RBC) in comparison with control group. In I. punctatus, Ht, Hb and RBC remained constant after 96-hour sublethal exposure. However, after the recovery period of 7 days a significant increase of RBC followed by reduction in mean corpuscular volume (MCV) and mean corpuscular hemoglobin (MCH) were observed in I. punctatus. The sublethal responses to phenol revealed erythropoeisis in I. punctatus and respiratory distress in P. mesopotamicus. P. mesopotamicus presented excessive skin and gills mucus throughout the 96-hour LC50 tests. Acute toxicity tests and hematological responses after exposure to sublethal phenol concentration could be successfully used as a biomarker of stress in fish and may be applicable to investigate others toxic agents.

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